Brake mechanism



Feb. 5, 1957 w. o. BECHMAN ET AL BRAKE MECHANISM 6 Sheets-Sheet 1 Original Filed April 19, 1950 2520822122715; j. flake)" 2612mm Jazgzi llzizzny "if m a Feb. 5, 1957 w. o. BECHMAN ET AL 2,780,319

BRAKE MECHANISM Original Filed April 19, 1950 I 6 Sheets-Sheet 2- Feb. 5, 1957 w. o. BECHMAN ET AL 2,780,319

BRAKE MECHANISM Original Filed April 19, 1950 6 Sheets-Sheet 5 a e2- 035cm Jag Q. lan l ZZZZZM 672721239 Feb. 5, 1957 w. o. BECHMAN ET AL BRAKE MECHANISM 6 Sheets-Sheet 4 Original Filed April 19, 1950 W. O. BECHMAN ET AL Feb.5, 1957 BRAKE MECHANISM e Sheets-Sheet 5 Original Filed April 19. 1950 Feb. 5, 1957 v w. o. BECHMAN ETAL v 2,780,319

BRAKE MECHANISM Original Filed April 19, 1950 6 Sheets-Sheet 6 a' wd a? m'zzzzm z/ #92150 United States Patent BRAKE MECHANISM William 0. Bechman and Harry A. Land, Chicago, and David Baker and William W. Henning, Riverside, 11]., asslgnors to International Harvester Company, a corporation of New Jersey Original application April 19, 1950, Serial No. 156,764, now Patent No. 2,716,907, dated September 6, 1955. Divided and this application November 9, 1953, Serial No. 390,962

9 Claims. (Cl. 188-72) This invention has to do with steering control apparatus for steemng-by-driving vehicles, and more particularly concerns improvements in steering brake engaging means together with means selectively controlling the engagement and engagement intensities of a plurality of. brakes for attaining diflierent speeds of vehicle propelling means at each side of the vehicle. The invention claimed herein is a division of Serial No. 156,764, filed April 19, 1950, now Patent No. 2,716,907.

Brake applying and control mechanism constructed in accordance with this invention is adapted for use in controlling the speed and turning radii of steering-by-driving vehicles having change-speed final drive gearing and brakes as that illustrated in U. S. Patent No. 2,496,429, issued February 7, 1950, in the name of David B. Baker et al. for Vehicle Change-Speed and Steering Gear. The present mechanism is related to an improvement over brake applying and control mechanism shown in U. S. Patent No. 2,468,628 issued April 26, 1949, in the name of William W. Henning, for Hydraulic Control System for Steering-By-Driving Mechanism.

Sfleering-by-driving vehicles have vehicle propelling means commonly in the form of self-laying tracks at opposite sides thereof. When these two propelling means are driven at the same speed they propel the vehicle in a straight course forwardly or rearwardly according to the direction in which the propelling means is driven. The course of the vehicle can be varied from a straight line by changing the relative speed of the propelling means. In the vehicle with which the present invention is associated the vehicle body has a customary final drive casing forming a rear portion thereof and containing two final drive change-speed transmission units having respective driven shafts and respectively drivingly connected with the two propelling means. The vehicle engine occupies a forward position on the vehicle body and the crankshaft of this engine is connected through a releasable main clutch with a main change-speed transmission unit. The driven shaft of this main change-speed transmission unit extends into the final drive casing where a driving connection is had with each of the final drive change-speed transmission units. These final drive transmission units are of the orbital gear type, each having two brakable disk alternatively holdable against rotation for causing the driven shafts of these final drive transmissions to rotate at relatively high or low speeds. Such brake disks are coaxial about the driven shafts respectively associated therewith and are spaced apart axially of these shafts. Also in coaxial axially-spaced relation with each of these sets of brake disks is a third disk rigidly secured to the associated driven shaft. The first two disks in each of these sets of brake disks are known as high and low speed transmission brake disks respectively whereas the third disk in each set is known as the driven shaft brake disk. When the two high speed brake disks are constrained against rotation and driving force is transmitted through the main clutch and the main transmission to the final .dn've transmissions, thevehicle .willv bev driven in a 2,780,319 Patented Feb. 5, 1957 ice straight course (forwardly or rearwardly dependent upon the setting of the main transmission unit) at relatively fast speed. Under these same circumstances except that the high-speed brake disks are released so they can turn freely and the two low-speed brake disks are constrained against rotation, the final drive transmissions will cause the propelling means at the sides of the vehicle to rotate at the same relative speed to cause strai ht line movement of the vehicle but more slowly. The vehicle can be braked to a stop or held on an incline against forward or rearward movement by applying braking force to the shaft brake disks while the transmission brake disks are released. The vehicle can be caused to change its course by selective engagement of different brake disks in the two brake disk sets thereby causing the propelling means sides of the vehicle to be driven at different speeds, or, either propelling means to be braked and held immovable while the other propelling means is power driven.

To facilitate the ease of steering and maneuvering the vehicle, hydraulic rams are used for engaging the various brakes. Two control levers, one for each set of the aforesaid brakes, are provided conveniently accessible to the operator. These control levers are placed side by side for rocking motion coaxially about an axis extending transversely of the vehicle. When these levers are in a forward position they condition a hydraulic circuit to energize rams for causing engagement of the high speed brakes, and when such control members are in a more rearward position the hydraulic circuit is conditioned for causing engagement of only the low speed brakes, and when the levers are in a rearmost position they cause engagement of only the driven shaft brakes.

Inasmuch as the transmission brake disks in each set are mechanically interconnected, undue brake wear would be incurred if they were simultaneously engaged. Consequently the control apparatus is so designed that a quick transfer is made between engagement of the transmission brakes in each set. The control members have definite high speed and low speed positions in which the high speed and low speed brakes associated therewith are respectively fully engaged. Shifting of these control members from either speed position to the other involves a quick complete change of brake engagement to avoid a concurrent engagement of the brakes in either set. However, subsequent to retraction of the control levers rearwardly beyond the low speed position which incurs disengagement of the low speed brake, it is usually desirable to only partially engage the shaft brakes. An object of this invention is the provision in the steering-bydriving control mechanism of this character of a hydraulic system operable under control of the manual control members to cause engagement of the shaft brakes with an intensity correlated with the distance these members are retracted into a braking range rearwardly of the low speed positions of these members.

A further object is the provision of a hydraulic control system under control of control members as aforesaid, including fluid pressure controlling valves operable to subject the shaft brake operating rams to fluid pressure of an intensity correlated with the distance of retraction of said members into the braking range, together with other manually-operated brake applying means alternatively operable through said valves for causing engagement of the shaft brakes.

A further object is the provision in connection with a final drive casing having final drive change-speed transmission units and their associated sets of brakes including shaft brakes mounted therein at opposite sides of the fore and aft median line of the vehicle, of power operated lost motion linkages connected with pivoted operators for the brakes, and a manually operated double lever structure pivotally mounted on the casing between the setsof brakes and having lost-motion thrustmembers inserted between respective arms thereof and the brake operators as an alternative means of manually applying theibrakes-independently of hydraulic power.

Still a further object is the provision of an improved steering-by-drivingcontrol according to the preceding object wherein the shaft brakes are operated by hydraulic rams in accordance with the pressure of fluid admitted through pressure control valves, together with means for operating said valves in accordance with the operation ofthe manually-operated thrust-members whereby power application of the brakes is incurred excepting in the case of hydraulic power failure.

Another object is-the provision of an improved mounting means for brake-operating members in the form of yokes, such means including a mounting bracket having a plurality of-brake shoe carrying yokes rockably mounted thereon between certain of the brake disks against which the brake shoes are frictionally engaged pursuant to rocking of the yokes.

These and other desirable objects inherent in and encompassed by the invention will be more readily conceived from the ensuing description, the appended claims and the annexed drawings, wherein:

Fig. 1 is a diagrammatic plan view of a steering-bydriving vehicle in the form of a crawler tractor, and illustrating the manner in which control apparatus constructed in accordance with this invention is mounted thereon.

Figs. 2 and 3 are respective counterparts of a fragmentary plan view of the final drive housing constituting the rear part of the tractor body shown in Fig. 1, these views being complementally assembled when the line CL along the righ-hand edge of Fig. 2 coincides with the line CL along the left edge of Fig. 3, these lines CL and CL coinciding with the longitudinal median line ML in Fig. 1. The Fig. 3 component of the Fig. l-Fig. 2 plan view is partly in section and partly diagrammatic for clarity of illustration.

Fig. 4 is a fragmentary vertical sectional view taken through the final drive casing substantially on the plane indicated by the line 4--4 in Fig. 1, this view illustrating the mounting of the brake operator members (yokes), the relation of these yokes to the transmission and shaft brake disks associated therewith, together with a part of the linkage for controlling the rocking of the brake operator members.

Fig. 5 is a fragmentary elevational view taken on the line 55 of Fig. 4 showing a portion of a final drive casing end wall and the position of brake strut and brake wear take-up adjusting means accessible for manipulation through openings in such wall.

Fig. 6 is a detailed sectional view taken on the line 66 of Fig. 5.

Fig. 7 is an enlarged perspective view of a sub-assembly including a frame having transmission brake operator members rockably mounted thereon.

Fig. 8 is a perspective view of the sub-assembly shown in Fig. 7 but taken from the opposite side thereof.

Fig. 9 is a diagrammatic view illustrating the pressure source of the hydraulic control system together with valves, hydraulic rams, brake operators and the final drive change-speed gearing for controlling the speed of the driven shaft which is drivingly connected with the propelilng means at the right side of the vehicle, as viewed in Fig. 1.

The crawler tractor 11, Fig. 1, in connection with which the preferred embodiment of the invention is herein illustrated, includes a body 12 having a diagrammatically illustrated engine 13 on its forward end, a final drive casing 14 at its rearward end and endless trends or tracks 15 and 16 at opposite sides of such body12. These endless tracks are independently driven by coaxial oppositely extending and independently drivable driven shafts 17 and 18. When the shafts 17 and 18 are driven at the same speed-in the same direction the tracks 15 and.16 will be driven at the same speedfor causing movement of the vehicle in a straight course. Veering of the vehicle from th straight course at selected angles of departure of for making a pivot turn is effected by driving the tracks at different speeds or by holding either of the tracks against movement while the other track is driven.

Power fromthe vehicle .engine 13 is transmitted through a main clutch (not shown but controlled by a pedal 16) and a main change-speed transmission (not shown) to a tail shaft 19, Figs. 1 and 9, which extends from said changespeed transmission into the final drive casing 14. A bevel pinion 21 on the shaft 19 drives a bevel gear 22 which is connected for rotation with van orbital gear carrier 23, Figs. 1 and 9, containing identical final drive change-speed gearing units 24 constituting change-speed power transmission mechanisms selectively arrangeable for transmitting driving force respectively to the driven shafts 17 and 18 at high or low speed or arrangeable in neutral. A portion of one of the final drive change-speed gearing units 24 is shown diagrammatically in Fig. 9 for driving the shaft 18. A complete steering-by-driving apparatus including both gearing units as 24 is shown and described in detail in the above mentioned Patent No. 2,496,429. It will suflice to here explain, therefore, that the gearing unit 24 is operable when a low-speed brake disk L is braked for holding it against rotation while disks H and B are free to rotate, the driven shaft 18 is caused to rotate at a relatively low speed and that when the high-speed brake disk H is braked for holding it against rotation while the disks L and B are free to rotate, the shaft 18 is caused to rotate at a relatively high speed. Brake disk B is connected for rotation with the shaft 18 so, of course, when braked, resists rotation of the shaft 18 and of the track 16 with which this shaft is drivingly connected. Inasmuch as the brake disks L and H of the steering-by-driving apparatus 25 are operable for selectively arranging the change-speed power transmitting mechanism 24 for transmitting driving force to the driven shaft 18 for causing this shaft to be driven at relatively high or low speeds, or to cause this mechanism to be in a neutral condition wherein no driving force is transmitted to the shaft 18, these disks L and H are referred to as the transmission brake disks. The disk B is referred to as the shaft brake disk.

Each of the brake disks B is frictionally engageable by the complemental action of an arcuate fixed brake shoe 27 mounted on an end wall 28 of the final drive casing and movable arcuate brake shoes 29 and 31 having friction faces 29 and 31 Figs. 9 and 7. These brake shoes 29 and 31 are prvotally carried upon a shaft brake operator in the form of a rockable yoke 32 which is pivotally mounted upon end portions 33 and 34 of a frame 35 by pivot pins 36 and 37 and a third pivot pin 38 carried by a center leg 39 of this yoke 32 and journaled in bearings 41 of apertured ears 42 mounted upon a horizontal bottom flange portion 43 of the frame 35. This horizontal flange portion 43 also has apertured cars 44 and 45 respectively adjacent to the leg ends of the yoke 32 for receiving inner ends of the pivot pins 36 and 37. The bearing apertures in the ears 42, 44 and 45 are coaxial with the bearing pins 36 and 37 secured in the frame end portions 33 and 34. A pivot shaft 51 has opposite ends mounted respectively in one leg of the yoke 3.2 and in the center leg 39 of such yoke. A similar pivot shaft, 51 extends between the center leg 39 of the yoke and the opposite end leg thereof for similar pivotal mounting of the brake shoe 31. Such pivotal mounting of the brake shoes 29 and 31 enables them to maintain the friction faces 29 and 31 in parallelism with and flatly engaged with the shaft brake disk B when pressed thereagainst as illustrated in Fig. 9.

Frame 35, Figs. 7 and 8, also serves as a support for a brake operator yoke 52 which has its two ends pivotally mounted. thereonby means of bearing pins 53 and 54 which are respectively carried in the end portions 33 and 34 of said frame, pin 53 being shown in Fig. 7 and pin 54 in Fig. 8. A brake shoe 55 is pivotally carried in the yoke 52 by pivot pins 56 and 57. There are two friction faces on the shoe 55, one face being designated 58 in Fig. 8 and the other 59in Fig. 9. When the yoke 52 is rocked clockwise, Figs. 4 and 9, about the fixed pivots 53-54, a segment of the shaft brake disk H becomes frictionally engaged between friction surfaces 59 and 61, the latter being on frame 35. When the brake operator 52 is swung counter-clockwise, Figs. 4 and 9, the friction face 58 is adapted to compress a section of the brake disk L against a friction face 62 carried on a brake shoe 63 pivotally carried upon coaxial pins 64 at opposite ends thereof and mounted in the legs of a brake reaction yoke 65 which embrace the shoe 63, one of the legs of the yoke 65 being shown in Fig. 4. Each leg of the yoke 65 carries a pivot pin 66 and these two pins 66 are journaled in bearings, not shown, respectively, upon the rear wall 67 of the final drive casing and the opposed forward wall 68, Figs. 3 and 4.

Brake operator yoke 32 is adapted to be operated either manually by the operation of the pedal 69, Fig. 9, or by a brake control hydraulic motor means in the form of a ram 71 energizable for applying braking force to the shaft brake operator 32 according to the magnitude of fluid pressure imposed upon such ram. Fluid pressure introduced into the ram chamber 72 through a port 73 will force a piston 74 endwise for imparting thrust against one arm 75 of a multi-arm lever structure 757 6 pivotally mounted upon a fixed pivot pin 77 secured to the final drive casing cover 78, Figs. 3 and 4. A balland-socket connection 79 is provided between a piston rod 81 of the piston 74 and the arm 75, Figs. 3 and 9. Arm 76 of the multi-armed lever structure 7576 has two sockets 82 and 83. Socket 82 receives a semispherical (ball) end 84 of a thrust link 85 which has an opposite ball end 86 disposed within a socket 87 of a socket member 87 carried in a boss 88 projecting upwardly from the lever 32; see Figs. 4, 7 and 8.

The force-transmitting power train including the thrust member 8!, the driving lever arm 75 of the lever structure 75-76, driven lever arm 76 of such lever structure and the thrust member 85 disposed in series between the ram piston 74 and the rockable brake-operating member 32 is duplicated on the opposite side of the final drive casing, as shown in Figs. 1 and 2 where corresponding parts are identified by the same respective characters with the addition of a prime. The various sockets for receiving the ball-like formations upon the ends of the thrust members 81 and 85 are sufficiently deep to facilitate telescopic lost motion of the parts at these ball and socket joints, thereby accommodating untrammeled operation of the brake-operating members 32 and 32' by a manuallyoperated linkage next to be described and also to accommodate substantial tolerance in the accuracy of the positions and dimensions of the rams, lever structures and brake-operating yokes 32 and 32.

A double-arm lever structure 91, Figs. 2, 4 and 9, is pivotally mounted in a bearing 92 on the final drive casing cover 78. The arms of this lever structure 91 are respectively designated as 93 and 94 and a spindle 95 extends downwardly from this lever structure into the bearing 92. Lever arm 93 contains a socket 96 for a ball 97 on the inner end of a thrust exerting structure in the form of a rod 98. The outer end of rod 98, Fig. 3, has a ball end 99 disposed in the lever arm socket 8 3. A thrust rod 98 corresponding to the rod 98 and assembled with corresponding elements designated by the same respective reference characters with the addition of the prime is connected between the lever arms 94 and 76'. When the double arm lever structure 91 is rocked counterclockwise, as viewed in Figs. 2 and 9, a thrust force can be transmitted through the thrust members 98 and 98 for rocking the yokes 32 and 32' for simultaneously apply ing braking force to the shaft brake disks B attire twe sides of the vehicle. Rocking of the double-arm lever structure 91 is manually effected through a horizontal lever 100, Figs. 1, 2, 3 and 4, to which manual force is applied through a brake pedal 69 and a tension rod 102, Figs. 1 and 3. A manually operated linkage, including the double arm lever 91, the thrust rods 98--98' and the ball and socket joints at the ends of these rods, contains sufficient telescopic motion in these joints to facilitate rocking of the brake-operating members 32--32 by force received from the hydraulic rams 7171' without incurring movement of the thrust rods 98-98 and the parts connecting them with the pedal 69. These ball and socket joints at the ends of the rods 9898 have the further advantage of being easily assembled and of accommodating substantial tolerance in the dimensions of and locations of the parts inter-connected thereby. This is a significant factor in view of the large size of the final drive casing and the practice of producing such cas ing and the parts mounted therein on various machines in difierent parts of the factory together with the imperativeness that the parts fit into a properly operating mechanism when put together on an assembly line.

Normally the shaft brake B is maintained in a dis engaged position by a spring 105, Fig. 4, which reacts between an end wall of the final drive casing cover 78 and the socketed member 87 mounted in the upper end of the brake operator 32. Socketed member 87 is screwthreaded at 106 into an internally threaded sleeve 107,

clamped into a split bore 108 in the projection 88 of the associated member 32. This facilitates adjustment of the brake-applying linkage by removing a screw plug 109, Figs. 4- and 5, from a threaded opening 111 in the associated casing cover end wall and thereafter inserting a square-ended 'tool into a square sectioned recess 112 in the socketed member 87 for rotating this member and changing its axial position in the sleeve 107 and correspondingly changing the rocked position of the brakeapplying member 32 relatively to the associated ram piston 74 and the brake pedal 69.

Access is also provided in the end wall of the final drive casing cover 78 for adjusting a strut 113 for bracing the center upper portion of the brake operator mounting frame 35, Fig. 4. This strut has a threaded inner end 114 meshed with threads in a threaded hole 115 in the frame 35. The outer end of this strut has a head 116 disposed Within a hole 117 of the casing cover end wall. A square recess 118 in the outer face of the strut head 116 is adapted to receive a square ended tool (after removal of a screw plug 119 from the hole 117) for rotating the strut to change the spacing of the head 116 from the frame 35. When the screw plug 119 is reinserted it assures placement of the head 116 against a shoulder 121 for rigidly maintaining the upper part of the frame 35 selectively spaced from the end Wall of the casing cover 7 8.

A second strut 122, Figs. 4 and 6, is connected between an upper mid portion of the brake reaction yoke 65 and the casing cover end wall. The inner end of the strut 122 has a threaded connection with the upper part of the yoke 65 similar to that at 114115 of the strut 113 with the upper portion of the frame 35, and the outer end of this strut 122 has an adjustment-facilitating connection with the casing cover end wall similar to that described for the strut 113. This description is therefore expedited by simply designating the connecting parts for the outer end of the strut 122 by the same respective reference characters used in connection with the strut 113 but with the addition of a prime. By adjusting the rotative position of the strut 122, the rocked position of'the brake reaction yoke 65 about the fixed journal pins 66 can be changed for changing the position of the friction surface 62. The initial adjustment of the brakes and subsequent adjustment to compensate for wear of the friction surfaces is thereby facilitated. Struts corresponding to 113 and 122 and their end connections above described are also -shown and described in detail in U.

provided forthe corresponding framesand brake reaction leversin that part of the steering 'by-driving apparatus in theleft'side of thefinal drive casing.

Transmission control hydraulic motor means in the form of a doublepiston hydraulic ram 110, Figs. 1, 3 and 9, is variably energizable when subjected to various statuses of pressure derived from a fluid pressure source 151'f0r'pla'cing thefinaldrive transmission'mechanism 24 on its corresponding side of the final 'drive casing in neutral, slow speed,'o1"high speed arrangements. A corresponding ram for the mechanism on the left side of the vehicle is designated 110 in Figs. 1 and 2. confining the description to that part of the final drive change-speed mechanism for the right side of the vehicle, since the left side-part is identical, the ram 110 is eooperable with a captive spring structure 112 Fig. 4, for controlling the pivoted'position of the brake operator member 52. This captive spring structure reacts against a wall 113 of the final drive casing cover 78while exerting force through a socketed cap 114 and a threaded cup-shaped member "115 to the upper end of the brake operator 52 for yieldably holding'said member in its clockwise position,-Fig. 4, to engage the highspeed brake H. The threaded member 115' has screw threads 116 meshed with threads in a threaded split opening 117 in the brake operator so that by rotation of the member 115 its position axially of the opening 117 can be changed. A ball end 118 of the member 115 telescopically rests in a semi-spherical seat 119 in the cap 114*.

Threaded member 115 contains a semi-spherical seat 121 within its inner end for receiving a ball end 122 of a strut member 123 having a ball outer end 124 received by a semi-spherical seat 125 of a lever arm 1126, Figs. 3, 4 and 9. The lever arm 126 is one component of a multi-arrn structure 126-127 having a second arm 127 pivotal about a fixed pivot pin 128 anchored in the final drive casing cover. Arm 127 contains a socket 129 for telescopically receiving a ball end 131 of a strut 132 having an opposite ball end 133 telescopically seated in a socket 134 in a rod 135 of a piston 136 of the ram 111 In reduction of fluid-under pressure through a port as 137 in a wall of the ram 110 causes development of fluid pressure in a chamber 138 forcing a piston 139 endwise against the piston 136 for moving the latter to a limit determined by abutment of an enlargement 141 of the piston 139 against an end wall 142 of the chamber 138. This concurrent advancement of the pistons 139136 causes clockwise pivoting of the lever structure 126127 far enough to retract the brake-operating member 52 into the neutral position against the force of the captive spring structure 112 thereby providing for both friction surfaces '58 and 59 being out of frictional engagement with the brake disks L and H. Subsequent introduction of'pressurefluid into the ram port 143, Figs. 3 and 9, will cause additional advancement of the piston 136 to cause pivoting of the brake operating member 52 further counterclockwise as viewed in Figs. 4 and 9 for engaging the low speed brake 1.. Use of the 'various telescopic ball and socket connections in the power transmitting linkage between the ram piston 136 and the brake operator member 52 accommodates substantial tolerance of accuracy in the relative positions and the dimensions of the connected parts.

A. source of fluid under pressure for operating the hydraulic rams is diagrammatically illustrated in Fig. 9 where such pressure source of fluid is generally designated 1'51. inasmuch as this pressure sourceof fluid is S. Patent No. 2.468.628. it will. suflice to explain that fluid (preferably oil) is withdrawn from a spring chamber reservoir 152 through a conduit 153 and a filter 154 into a constantly running pump 155, preferably mounted on and driven from the vehicle engine 13, Fig. 1. Thisfiuid is discharged from the pump through a check valve 156, conduit 157 and a pressure controlling device 158 and a conduit 159 into an accumulator chamber 161. A compression plunger 162 of the accumulator is urged compressiblyagainst the fluid in the chamber '161 by a spring 163'in the-spring chamber reservoir 152. After the accumulator chamber 161 is expanded attendant to the pressure therein attaining a predetermined maximum, the pressure controlling device 158 will terminate delivery through the conduit 159 and cause by-pass directly into the reservoir 152 through a low pressure by-pass conduit 164. While this condition prevails the constant delivery pump will operate under low-pressure conditions.

Subjection of the transmission control hydraulic motor means 110 and of the brake control hydraulic motor means 71 to the pressure of fluid at the pressure source 151 is had under control of a manually-operated control means contained in a control casing 171, Figs. 1, 2, 3 and 9. This casing contains two sets of valves and mounts two valveadjusting control members 172 and 172 respectively for said sets of valves. One set of valves and the associated control member 172 is for the final drive change-speed power transmitting mechanism at the left side of the vehitcle and the other set of valves and associated control member 172 is for the final drive change'spee'd power transmitting mechanism at the right side ofthe-vehicle. The set of valves associated with the control member 172 is illustrated in Fig. 9.

The twosets of valves and the two control members 172472 are identical. Referring, therefore, to Fig. 9, the set of valves there shown includes a pressure reduction-valve 173, a high-speed brake releasing valve 174, a low-speed brake engaging valve and a shaft brakeengaging'valve 176. The valves 173, 174 and 175 are shown and described in detail in U. S. Patent 2,468,628. Details of the valve 176 are described and claimed in copending application, Serial No. 95,559, filed May 26, 1949, in the name of William W. Henning. Pressure reduction valve 173 supplies fluid from the source 151 thorugh conduits 177 and 178 at a reduced pressure to the valve 175 so that when this valve 175 is open the fluid at reduced pressure will be introduced into-the ram 110 through a conduit 179 and the port 143 above the piston 136 at less pressure than fluid introduced through the valve 174, conduit 181 and the port 137 into the chamber138 above the piston 1'39 wherefore the pressure above the piston 139 will-prevail over the pressure below such piston and retractive movement of the piston 139 will not occur with attendant delayed action inthe advancement of the piston 136 when it is desired to engage thelow speedbrake L.

Valve adjusting control member'172 is mounted upon one end of a shaft 182,Fig. 9, withwhich it is connected for rotation. A gear segment 183 is also connected'for rotation with the shaft .182 and meshes with a second segment gear 184 which is mounted on a shaft 185 which connects this segment gear and a control cam 186 for rocking in unison. Cam 186'has a short radius profile 187 which is separated from a long radius profile 188 by'a shoulder 189. Profiles 187 and 188 are cooperable with a follower 191 on an axially movable valve plunger 192 of the highspeed hold-out valve 174. This valve is held in the open position illustrated while the profile 188 registers with the follower 191, and-'a spring 193 movesthe plunger 192 to the-right for closing the valve 174=Whenthe short radius profile 187 registers with the follower 191. A cam-lobe 194 and a profile 195 are alternatively registerable with a follower 196 on a valve plunger 197-of the valve 175. When profile-195 registers with thefollower 196 a spring 198 is operable to'hold the plunger 197 retractedfor closing the valve 175 but when the lobe 194 registers with the follower 196 the plunger is advanced to the left for opening the valve, establishing communication between the reduced-pressure conduit 178 and the conduit 179for introducing pressure'fluid above'the piston 1'36 forengaging the low-speed establishing brake L.

A detent ball 199 is urged radially'inwardly of the'cam '186by a spring 201. When the'control'member'172 moves in the shaft brake engaging range B'B a profile 202 coi the profile 188 axial with the cam registers with the detent ball 199. Movement of the control lever 172 to position L places a detent notch 203 in registry th the detent ball 199 simultaneously with placing the lobe 194 in registry with the low-speed valve plunger follower 196 while a portion of adjacent to the shoulder 189 remains in registry with the high-speed hold-out valve plunger follower 191. The detent ball 199 thus cooperates with the notch 203 for retaining the cam in this low-speed establishing position.

' Upon manual movement of the lCOIltI'Ol lever 172 into position H, a detent notch 204, in cam 186 is brought into registry with the detent ball 199 incident to the cam lobe 194 passing from beneath the follower 196 and bringing the profile 188 into registry with this follower, and the short radius profile 187 into registry with the follower 191. In this manner the valves 17 4 and 175 are conditioned to connect the conduits 181 and 179 with the low-pressure conduit 205 leading back to the reservoir 152, thereby permitting both chambers of the ram 110 to exhaust and permitting the brake operator 52 to be rocked by the force of the captive spring unit 112 Fig. 4, clockwise for engaging the high-speed brake H and establishing the high speed power transmitting condition of the final drive changespeed power transmission mechanism 24.

I The control means, in the casing 171, for the final drive change-speed transmission mechanism 24 is shown with the valve-adjusting control member 172 in the driven shaft braking range B'B. The transmission mechanism 24 is then in neutral because the valve 174 is open to direct pressure fluid into chamber 138 of motor 110 to hold pistons 139 and 136 in the positions shown for rocking the brake operator 52 into the position where neither transmission brake L nor H is engaged. As the control member 172 is retracted from the position L and commences to enter the brake range B'B at point B, a finger 206 abuts against a head 207 on the lower end of a lever 208 mounted upon a fixed pivot 209. At this time a spring 211 will be maintaining the lever retracted with apad 212 thereon in engagement with a lever 213 which is fixed upon a rockable shaft 214 and rocked to a retractive position with a pad 215 thereon engaged with the casing front wall 216. Continued retraction of the control member 172 from position B into the range B'B will cause the cam finger 206 to move the lever head 207 clockwise incident to compressing the spring 211 and moving the control plunger 217 of the shaft brake valve 176 to the left, as viewed in Fig. 9, to cause admission of fluid from the pressure source and a conduit 218 into a conduit 219 at a pressure correlated with the leftward movement of the plunger 217 into the range B'B. The detent ball 199 will slide along the cam profile 202 attendant to rocking motion of the cam 186. In this manner fluid pressure through the conduit 219 is introduced into the shaft brake ram chamber 72 for engaging the shaft brake B with a pressure intensity correlated with the distance of retraction of the control member 172 into the braking range B'B. Inasmuch as the spring 211 reacts upon the lower end of the lever 208 and hence against the cam finger 206 for reestablishing registration of the detentnotch 203 with the detent ball 199, this spring 211 constitutes means for yieldably rotating the control member 172 a'dvancively from the braking range and operable to so advance such control member incident to manual release thereof while it is in such braking range.

The brake pedal 69, in addition to being connected by a rod 102 with the double-arm lever structure 91,

Fig. 9, for mechanically rocking the shaft brake operator members 32 in the event of hydraulic pressure failure, is also connected by a diagrammatically presented linkage 221 with the cross shaft 214 in the forward part of the control means casing 171 whereby depression of the pedal 69 rocks the shaft 214 and the arm 213 in the direction for swinging the lever 208 clockwise for operating the pressure control valve 176 to cause introduction of fluid into the shaft brake ram chamber 72 at a pressure correlated with depression of the brake pedal, wherefore this pedal is operable to cause hydraulic power operation of the shaft brake. A linkage 221' corresponding to the linkage 221 connects the brake pedal 69 with the brake control means for the other side of the vehicle so that depression of the brake pedal causes simultaneous hydraulic power application of both shaft brakes B. The linkages 221 and 221 are adjusted so as to cause the opening of the pressure controlling valves 176 (respectively for the two sides of the vehicle) and the introduction of brake-applying pressure in the brake ram chambers 72 prior to exertion of manual force through the thrust members 9898 so the brake pedal is easiiy depressed in the absence of hydraulic pressure failure.

Having thus described a single preferred form of the invention with the view of clearly and concisely illustrating the same, we claim:

1. In brake mechanism for oppositely extending shafts journaled in a casing, brakes in said casing respectively associated with said shaft for controlling the speed of the shafts when braking force is applied to such brakes, and brake-operating yokes respectively associated with said brakes and rockable about axe extending transversely of said shafts to apply said brakes: the combination of hydraulic rams mounted on the casing and containing pistons with their principal axes extending transversely of said shafts, multi-arm lever structures mounted on the casing for pivoting about axes extending transversely of said shafts, each lever structure having an arm extending transversely of said shafts and spaced axially of the shafts from an associated one of said yokes and having an arm spaced axially from the piston of an associated one of said rams, thrust rods disposed respectively between the ram pistons and the lever structure arm spaced axially therefrom, additional thrust rods disposed between the other lever structure arms and the brake-operating yokes respectively associated therewith, and means for controlling pressure fluid energization of such rams for causing them to transmit brake-applying rocking force to said yokes through their associated lever structures and thrust rods.

2. The combination set forth in claim 1 wherein there are telescopic ball and socket connections respectively between the ends of said thrust rods and their associated ram pistons and lever structure arms to accommodate substantial tolerance in the accuracy of the. positions and dimensions of said rams, lever structures and yokes.

3. In brake mechanism for oppositely extending shafts journaled in a casing, shaft brakes in said casing respectively for said shafts, brake operating members spaced apart axially of said shafts, said members being respectively operable laterally of said brakes and rockable about axes extending transversely of said shafts for engaging said brakes, a double arm lever structure pivotally mounted on said casing between the brake operating members for moving oppositely extending arms of such structure concurrently in opposite directions axially of the shafts respectively toward the brake operating members, thrust members disposed respectively between said arms and the brake operating members for transmitting force from the lever structure to such members for applying the brakes pursuant to pivoting of the double arm structure, and telescopic ball and socket joint means connecting the ends of said thrust members with their associated lever structure arms and with the rockable brake operating members to accommodate substantial tolerance in accuracy of dimensions and the relative location of the double arm structure and the rock-able members.

4'. In brake mechanism for shafts journaled in a final drive casing of a steering-by-driving vehicle and projecting perpendicularly to and oppositely from a fore and aft median line of such casing, shaft brakes in said casing respectively for said shafts, brake operating members spaced transversely of the casing on opposite sides of 'to being rocked toward such wall, said lation of one side of 21 the fore and aft median line thereof and rockableapart about axes extending transversely of said shafts for applying 'said brakes, hydraulic rams mounted on the easing at opposite sides of the median line; force transmitting power trains between the ram and their associated brake operating members, each power train including a lever structure pivotally mounted in said casing at a respective side of said median line and pivotal about an axis extending transversely of said shafts, such lever structure having a driven arm spaced laterally inwardly of the casing from the associated one of said brake applying members and having a driving arm spaced axially from its associated one of said rams, a thrust rod disposed between the associated ram and the driving arm of the lever structure, a thrust rod disposed between the driven arm of the lever structure and the associated brake operating member, each ram being operable when energized by hydraulic pressure to exert brake-applying rocking forcethrough its associated power train to the associated brake operating member; a double arm lever structure pivotally mounted on said casing between the brake operating members and for moving oppositely extending arms thereof concuirently in opposite directions transversely of the casing respectively toward the brake operating members; and thrust exerting structures disposed respectively between said arms of the double arm structure and the brake operating members for transmitting force from the double arm structure to such members for applying the brakes pursuant to pivoting of the double arm structure, and said thrust exerting structures being distendable to accommodate substantial tolerance in the dimensions and the relative spacing of the double arm structure and the rockable brake operating members, and to also accommodate rocking of the brake operating members by force received through said power trains from the rams without attendant pivoting of the double arm structure.

5. In mechanism for selectively braking coaxial axiallyspaced brake disks disposed in a casing having opposite side walls on opposite sides of the common axis of said disks and an end wall extending between such side walls, a frame extending between two of the disks and having ends mounted upon said opposite walls of the casing, a yoke disposed between .a side of said frame and a face of one of said disks and having its leg pivotally mounted upon end portions of said frame to facilitate rocking of the yoke about an axis extending transversely of the disk axis, a friction shoe embraced by legs of said yoke and pivotally mounted thereon about an axis extending in parallelism with the pivot axis of said yoke while disposed in opposed contiguity with said disk face, the casing end wall having a friction face in opposed contiguity wit-h the opposite face of said disk, said yoke being adapted to compress the one disk between said shoe and the friction face of the casing end wall pursuant frame having a friction face on the opposite side thereof in opposed resecond of said brake disks, a second-yoke disposed on the opposite side of the second disk and having its legs pivotally mounted in the end portions of said frame to facilitate rocking of this yoke about an axis in parallelism with that of the first yoke, a second friction shoe embraced by the legs of the second yoke and pivotally mountedthereon about an axis in parallelism with the pivot axis of said yoke, and the second'shoe being operable complementally with the friction face of the frame to compress a-segment of the second brake disk therebetween pursuant to rocking of the second yoketoward the frame.

6. In mechanism for selectively braking coaxial axiallythereof about an axis in .ing fromthe exterior side of said spaced brake disks, a brake-yoke-carrying frame including a substantially flat body disposable between two of said disks in parallelism therewith and having end portions spaced apart circumferentially of the disks; a pair of brake-shoe-carrying yokes on opposite sides of said flat body and each having its legs pivotally mounted respectively in the frame end portions to accommodate rocking of the yokes about axes extending lengthwise of the frame toward and away from their sides of the flat body; and brake shoes for said disks, and said brake shoes being respectively embraced by said yokes and pivotally connected therewith for adjustment about axes substantially parallel with the axes about which the yokes are rockable.

7. A brake shoe assembly comprising a yoke-carrying frame having an elongated plate-like body with opposite end portions and a pressure receiving face extending between such end portions, said end portions containing coaxial bearings and said body having a third bearing between and coaxial with said end portion bearings, a yoke .at a side of said body and having opposite leg with their ends pivotally mounted on said end portion bearings, said yoke also having a center leg pivotally mounted on the third bearing of said frame, brake shoes respectively embraced between the outer legs of the yoke and said center leg, and bearing mean on the legs of said yoke for pivotally mounting said brake shoes about axes in parallelism with that of the coaxial bearings on said frame, and'said yoke being rockable in the frame bearings to carry said brake shoes alternately toward and away from'said pressure receiving face.

8. The combination set forfh in claim 7, wherein an opposite face of said frame body constitutes a friction brake surface, wherein there is a second yoke on the op- .posite side of said body and having its legs pivotally con- :nected with the end portions of said frame for rocking movement about an axis in parallelism with that of said coaxial bearings, and a brake shoe embraced by the legs of the second yoke and pivotally mounted on the legs parallelism with the rocking axis of such yoke, and said second yoke being adapted to move the brake shoe'thereon alternately toward and away fromsaid friction surface pursuant to rocking of the yoke.

9. The combination set forth in claim 7, wherein there is a final drive easing of a steering-by-driving vehicle, such casing having front and back side walls and a laterally disposed end wall extending between the side walls, said brake shoe assembly being disposed within said casing with the end portions of said frame secured respectively to the front and back walls, said end wall having an opening, and lengthwise adjustable strut means extending from the end wall opening to an intermediate portion of the plate-like body and interconnecting said wall and said body, and means accessible through said openend wall for adjusting the length of said strut.

References Cited in the file of this patent UNITED STATES PATENTS 1,171,655 Roach Feb. 15, 1916 1,673,713 Smith June 12, 1928 1,855,965 Hildebrand et a1 Apr. 26, 1932 1,940,845 Conner et al Dec. 26, 1933 1,947,272 Napolitan Feb. 13, 1934 1,959,049 Buus May 15, 1934 2,286,517 Tack June 16, 1942 2,424,922 Sadon July 29, 1947 

